The present invention, relates to a toner transporting device for transporting toner to a position just before the developing roller in a developing unit, and more particularly to a toner transporting device capable of loosening soft blocking toner lumps.
As a developing unit used in a xerographic copying machine, a printer, or the like, there is known a developing unit associated with a toner storage means. In this type of the developing unit, toner is supplied from the toner storage means into the developing unit by means of a toner transporting means. Generally, the toner transporting means consists of a toner transporting pipe, for example, which couples the toner storage means with the developing unit, a toner transporting auger which is located in a toner transporting path of the toner transporting pipe, the toner storage means, or the like.
In high temperature and high humidity conditions, when toner is transported from the toner storage means to the developing unit, toner particles attract to each other by extremely weak forces, to thereby form lumps of toner, viz., so-called soft blocking toner. To supply toner from a toner cartridge to the toner storage means, the toner cartridge is set to the copying machine. In this case, if the toner cartridge to be set is left unused for a long time, and it is set to the machine in a state that it is unsatisfactorily shaken, this soft blocking phenomenon of toner takes place.
The cohesive force of the soft blocking toner lumps is weak, and the toner lumps are fragile. However, sometimes the soft blocking toner lumps are supplied to the developing unit while not being pulverized by an agitating member of the toner storage means or the toner transporting means. The soft blocking toner lumps, after transported to the developing unit, are frequently transported to the developing roller while not being pulverized by the agitating member in the developing unit. The toner lumps thus transported appear as black dots on the developed image. The black dots greatly deteriorates the picture quality of the reproduced picture.
The picture quality deterioration problem by the soft blocking phenomenon of toner more frequently arises in the copying machine operating at high speed for image forming. The reason for this will be estimated such that in the high speed copying machine, a large amount of toner must be transported, for unit time, from the toner storage means to the developing unit, and as a result, the developing unit, the toner transporting means, and their related components are designed while placing an emphasis on the toner transporting performances. Recent tendency of a further reduction of toner particle diameter makes it easy for the soft blocking phenomenon to take place. In this respect, one will encounter with the picture quality deterioration problem more frequently.
A unique toner transporting device for preventing the toner blocking phenomenon taking place when toner is collected from the photo receptor by the cleaning unit and transferred to the developing unit is proposed by the applicant of the present patent application (Published Unexamined Japanese Patent Application No. Sho. 61-169422). In this device, a plate spring is provided at the coupling part of the toner transporting pipe with an auger in a state that the tip of the plate spring comes in contact with a spiral when the auger is turned. When the auger is turned, the plate spring is snapped with the spiral, to thereby vibrate. By making use of the vibration, the toner blocking phenomenon is prevented from taking place at the coupling part of the transport pipe, thereby ensuring a good toner transportation.
The toner transporting device with the plate spring is suitable for pulverizing large blocked toner lumps, but is unsuitable for pulverizing small toner lumps of which the diameter is several mm or smaller. The toner transporting device has such a structure that the plate spring is brought into contact with the auger spiral. Because of this structure toner is attached to the contact portion, to thereby form a lump of toner. Further, the contact of the plate spring applies a load to the. auger. This structure is disadvantageous particularly in transporting a large amount of toner.